 <!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        #box{
            width: 500px;
            height: 100px;
            border: 2px solid rosybrown;
        }
    </style>
</head>
<body>
    <input type="text" id="tt">&nbsp;
    <button  onclick="fn()">复制</button>
    <div id="box">
            
    </div>
    <script >
        function fn() {
            var div=document.getElementById('box')
            div.innerText='';
            var txt=document.getElementById('tt').value;
            var newh2=document.createElement('h2')
            var dd=document.createTextNode(txt);

            newh2.appendChild(dd) 
            div.appendChild(newh2)
        }
      
      
    </script>
</body>
</html>